Remote-control units for cranes and the like are generally well known. Typically, present remote-control systems for cranes include about 30 feet of electric, multiconductor wire cable connected to a hand-held, remote-control box which contains a plurality of electrical switches. The other end of the cable is connected to a control circuit on the chassis of the crane for controlling the various operations of the boom, trolley, and hoist on the crane. In this manner, when the operator actuates an electrical switch on the remote-control box, it energizes one of the control circuits to operate a particular component of the crane, such as moving the boom, or moving the trolley, or moving the hoist.
Although such an arrangement is generally satisfactory from an operational standpoint, there are certain drawbacks. For example, the remote-control box and cable, as well as the crane, are all electrically conductive. Therefore, during operation of the crane, if the operator inadvertently causes the boom to hit a high-voltage electric line, it will discharge through the crane and electric cable directly to the operator holding the remote-control box. As a result, the operator receives a large electrical shock and may be injured or killed. As such high-voltage lines are a common occurrence at work sites which employ such cranes, it is not uncommon for the operator of the remote-control unit to be injured as a result of the boom inadvertently striking a high-voltage line.
One possible solution would be to insulate the entire remote-control unit which is being held by the operator. However, this would make the remote-control unit too bulky. Moreover, there is no practical way to sufficiently insulate each of the individual switches on the remote-control box.
Another attempted solution has been to employ a fiber-optic remote-control unit with converters for converting the light signals to electrical signals. However, such an arrangement has been found to be too delicate and unreliable and prone to frequent breakdowns.
Accordingly, it would be highly desirable to provide an arrangement for a remote-control unit for a crane or the like which completely eliminates the possibility of the operator of the remote-control unit receiving an electric shock when the boom strikes a high-voltage line, and to provide such an arrangement which is both economical and reliable.
Broadly, it is an object of the present invention to provide an improved remote-control unit for a crane which satisfies one or more of the foregoing objectives. Specifically, it is within the contemplation of the present invention to provide an improved remote-control unit for use in such devices as cranes, shovels, and the like which eliminates the possibility of the operator of the remote-control unit being subject to an electric shock.
It is a further object of the present invention to provide an improved remote-control unit which is completely insulated from the crane and the electrical control circuit mounted on the chassis of the crane.
It is a still further object to provide an improved remote-control unit which is economical, reliable, and able to withstand tough field conditions and inclement weather conditions.